In recent years, looking toward next-generation mobile communication systems, studies have been conducted on radio transmission methods suitable for high-speed packet transmission capable of achieving data rates in excess of 100 Mbps, for example. Broadband is necessary for the frequency band used for such high-speed transmission, and the use of a bandwidth on the order of 100 MHz has been studied, for example.
In mobile communications, when this kind of broadband transmission is performed using a single carrier, BER (Bit Error Rate) performance may deteriorate significantly as a result of interference due to multipath propagation (delayed waves). Propagation paths in which multipath propagation is present are subject to frequency selective fading—that is to say, a property of such propagation paths is that fading fluctuation differs according to frequency.
Single-carrier frequency equalization technology has been studied as a technology for eliminating the effects of multipath interference and reproducing a waveform. This technology is an equalization technology that can be implemented with a simple configuration. Also, equalization processing is performed on a signal transmitted by means of a single carrier by multiplying the inverse characteristic of a propagation path frequency characteristic estimate by a received signal in the frequency domain (see Non-patent Document 1, for example). Furthermore, an advantage of this technology is that, since transmission is performed using a single carrier, the PAPR (Peak to Average Power Ratio) is lower than in multicarrier transmission, and an amplifier with a wide linear region is not as necessary as in a multicarrier transmitting apparatus. Non-patent Document 1: “Frequency Domain Equalization for single-Carrier Broadband Wireless Systems”, IEEE Communications Magazine, April 2002, pp. 58-66